1. Field of the Invention
The present invention relates to an electrical connection and a method for making the same.
2. Description of the Prior Art
Electrical connection between substrates respectively carrying electrode arrangements has been made through FPC (Flexible Print Circuit). This connection is illustrated in FIG. 1. A substrate 7a is provided with an electrode arrangement. The electrode arrangement 8a consists of a number of electrode strips 8a which are desired to make electrical connection with corresponding electrode strips 8b provided on another substrate 7b. An FPC 9 comprises a flexible sheet made from polyimide carrying a number of conductive strips 10 corresponding to the strips of these substrates 7a and 7b. The coupling of the strips 10, 8a and 8b of the sheet and the substrates is made through an anisotropic conductive films 11.
This method of making electrical connection includes the following shortcomings. First, since the connection is made through an FPC, there are two coupling sites which require much care and processes as compared with the case of a single site connection. The possiblity of connection error is also doubled. Second, the FPC is adhered to the substrates at a high temperature under pressure. The flexible sheet is thermally expanded during the thermal treatment, and the alignment of the conductive strips with the corresponding strips of the substrates is often sheared, resulting in disconnection or connection error. Third, the FPC sometimes comes off from the substrate when external force is applied just after the connection is completed.
These conventional disadvantages are considered originating from the structure of the anisotropic conductive film. FIG. 2 is an explanatory view showing the conventional structure of the anisotropic conductive film. The film is comprised of a sheet 11a of adhesive in which a large number of conductive particles 11b are dispersed uniformly. Because the conductive particles can not be deformed, the electrodes 10 and 8a are easily disconnected from the particles when the surrounding temperature changes and they are thermally expanded or contracted with reference to the diameter of the particles.